JPH0327774A - Discharge circuit - Google Patents

Abstract

PURPOSE:To improve the safety of an apparatus by discharging a capacitor charging through forming a discharge circuit only during a nonconducting period. CONSTITUTION:A power circuit is composed of an AC power supply 1, a power switch 2, a diode stack 3 constituting a full-wave rectifier circuit, and smoothing capacitors C1-C3 to control a relay 5 by a relay control circuit 4 to discharge a capacitor charge into a discharging resistor R1. The relay control circuit 4 is composed of a photocoupler 6, transistors 7-9, etc. Then, one side of the discharging resistor R1 is opened simultaneously with starting of the operation of the power circuit and closed simultaneously with stopping of the operation of the circuit to discharge the capacitor charge.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a discharge circuit of an electric circuit, and more particularly to a discharge means of a discharge circuit.

[Prior Art] In a discharge circuit of an electric circuit, for example, in the case of an inverter control device, as shown in FIG. After being full-wave rectified and smoothed by a smoothing capacitor CI-C3, it is output to a subsequent inverter circuit (not shown), but a discharge resistor R1 is connected between the positive and negative poles on the output side, and the power switch 2 is opened, the charges accumulated in the capacitors 01 to C3 are discharged via the discharge resistor Rl.

[Problem to be solved by the invention]

However, as mentioned above, a discharge resistor simply connected between the positive and negative poles of an electric circuit is not only used after the circuit stops operating.
Since discharge is always performed during circuit operation, power is wasted, and in order to reduce this wasted power consumption, the resistance value of the discharge resistor must be set large.

If the resistance value of the discharge resistor is increased, the discharge time after the circuit stops operating will take a long time, from several tens of seconds to one minute, and there is a risk of electric shock if service work is inadvertently started immediately after the power is turned off. There were also safety issues during service.

Therefore, it is an object of the present invention to solve these problems and provide a discharging circuit that can save unnecessary power during circuit operation, and can quickly discharge the charge accumulated in the capacitor after circuit operation is stopped. .

[Means to solve the problem]

The present invention has been made to solve the above problems, and includes a power switch provided on the human power side of a power supply circuit that converts AC power into DC power and smoothes the DC power using a smoothing capacitor. A relay contact is interposed on one side of the discharge resistor coupled to the output side of the power supply circuit, and a photocoupler is provided on the input side of the power supply circuit that is driven when the power switch is turned on, and a photocoupler that is driven when the power switch is turned on. a first transistor that operates in response to a signal from the differentiating circuit sent out from the differential circuit; a second transistor controlled by a signal from the integrating circuit sent out in conjunction with the operation of the first transistor; A relay control circuit consisting of a relay that operates based on a signal output in accordance with the operation of the transistor No. 2 and can open the relay contact is provided. [Function] With the above configuration, one side of the discharge resistor is opened when the power supply circuit starts operating, and is closed when the operation is stopped, thereby discharging the charge accumulated in the capacitor.

〔Example〕

An embodiment of the present invention will be described below with reference to FIGS. 1 and 2. In Figure 1, 1 is an AC power supply, 2 is a power switch, and 3
is a diode stack that constitutes a full-wave rectifier circuit with multiple diodes, C1 to C3 are smoothing capacitors for smoothing the full-wave rectified power, and R1 is for discharging the charges accumulated in the smoothing capacitors C1 to C3. 4 is a relay control circuit that operates in accordance with the opening and closing of the power switch 2, and 5 is a relay provided with a relay contact 5a.

The relay control circuit 4 includes a photocoupler 6 that operates using half-wave rectified power, and a differentiation circuit (not shown) that differentiates a pulse signal output in response to the operation of the photocoupler 6.
, a transistor 7 that operates in response to a differentiated signal, an integrating circuit (not shown) that integrates an output signal from the transistor 7, a transistor 8 that operates in response to an integrated signal, and a transistor 8 that operates in response to an integrated signal; A transistor 9 drives the relay 5 using an output signal from the transistor 8. A more detailed explanation of the relay control circuit 4 is as follows.
A protective resistor R2 and a diode DI for half-wave rectification are connected in series between terminal a of the photocoupler 6 and one end of the AC power source 1, and a lead wire or the like is connected between the terminal b and the power switch 2. Terminal C is coupled to the DC power supply line (Vcc) via resistor R3, and terminal d is grounded. A differential circuit is provided between the terminal C and the base of the transistor 7, which includes a capacitor C4 and a resistor R4 coupled in series, and a resistor R5 coupled between the base and the ground circuit.

The collector of the transistor 7 is connected to a DC power supply line via a resistor R6, and the collector is grounded.

Between the collector of the transistor 7 and the base of the transistor 8, there is a resistor R7 connected between both poles, and a resistor R7 connected between the collector of the transistor 7 and the base of the transistor 8.
An integrating circuit consisting of a capacitor C5 and a resistor R8 coupled in series between the collector of the transistor 8 and the ground circuit is provided, and a resistor R9 is coupled between the base of the transistor 8 and the ground circuit. The collector of the transistor 8 is connected to the DC power supply line via a resistor RIO, and the emitter is grounded. The collector of transistor 8 and the base of transistor 9 are connected by a signal line, and the collector of transistor 9 is connected to resistor R.
It is connected to the DC power line through the ll, and the vine is grounded. One end of the relay 5 is connected to the collector of the transistor 9, and the other end is connected to the DC power supply line via a resistor RL2.

The structure of the discharge circuit has been described above, and the operation will be explained below.

When the power switch 2 is turned on, the voltage is rectified by the diode stack 3, and the voltage after rectification is passed through the smoothing capacitors 01 to C.
After being smoothed by 3, it is output to a subsequent load @ (not shown) from the output end indicated by the arrow. At the same time, the diode D1 of the relay control circuit 4 also operates, and the half-wave rectified power is applied to the terminal a of the photocoupler 6. Since the photocoupler 6 repeatedly turns ON and OFF by receiving the half-wave rectified power, a pulse signal as shown in FIG. 2A appears repeatedly at point A on the terminal C side. This pulse signal is C4, R4. The signal is differentiated by a differentiating circuit consisting of R5, and a signal as shown in FIG. 2B is input to the base of transistor 7.

This signal drives transistor 7 to switch, and the potential at point C after passing through the integration circuit is
OV when in N state, time constant τ found by ((R6+R8) XC5) when +- transistor 7 is in OFF state
increases accordingly.

However, as shown in FIG. 2C, the time constant τ is set so that the potential at point C does not increase to a voltage that can drive the transistor 8, so the transistor 8 remains in the OFF state.

Therefore, the potential at point D is determined by the resistance R as shown in Figure 2D.
It is pulled up by IO, and transistor 9 maintains the ON state. When the transistor 9 is turned on, the potential at point E in FIG. 1 decreases, so the relay 5 is driven, and as the relay 5 operates, the relay contact 5a is switched and the discharge circuit provided with the resistor R1 is opened. On the other hand, when the power switch 2 is turned off, the photocoupler 6 is turned off, so the potential at point A remains pulled up as shown from the center to the right of FIG. 2A.

Therefore, the potential at point B is ((R3+R4+1?5)
It decreases to 0 according to the time constant τ determined by XC4).

When the potential at point B drops below the Vbe voltage of transistor 7, transistor 7 is turned off.

From this point on, the potential at point C changes as shown in Figure 2C ( (
R6+R8) increases according to the time constant τ determined by XC5).

When the potential at point C increases above the Vbe voltage of transistor 8, transistor 8 is turned on, and the potential at point D becomes QV as shown in FIG. 2D.

Therefore, the transistor 9 is turned off, and the potential at point E rises as shown in Figure 2, so the relay 5 is turned off, the relay contact 5a is switched to the resistor Rl side, and the voltage is accumulated in the smoothing capacitors 01 to C3. The charge that is present is discharged.

In addition, each part before the power switch 2 is turned on (from point A to
Since the potentials at point E) are all 0■, the relay 5 is turned off, and the circuit of the discharge resistor Rl is in a closed state.

In this state, when the power switch 2 is turned on, the potential of each part changes as shown in FIG. After about 20 m-sec, it is turned on and the circuit of the discharge resistor R1 is released. Furthermore, when the power switch 2 is turned off, the relay 5 is turned off approximately 30 m-sec later as shown in FIG. 2, and the circuit of the discharge resistor R1 is closed.

〔Effect of the invention〕

According to the circuit structure explained above, the discharge circuit can be activated only when no current is applied to discharge the charge accumulated in the capacitor, so it is possible to discharge the electric charge accumulated in the capacitor, which is different from the conventional discharge circuit in which a discharge resistor is always connected. Compared to this, there is no wasted power, and the value of the discharge resistance can be set to a small value, which greatly shortens the discharge time, eliminates the risk of electric shock, etc. at the beginning of service work, and improves safety. It has the effect of improving sexual performance.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing an embodiment of the present invention, FIG. 2 is a waveform diagram for explaining the operation of the same embodiment, and FIG. 3 is a circuit diagram showing a conventional example. In the diagram, l..1.1 AC power supply, 2..1 power switch, 3.
--- Diode stack, 4--- Relay control circuit, 5--- Relay, 5a-- Relay contact, 6
-・-Photocoupler, 7-9...Transistor, C1
~C3...Sliding capacitor, C4~C5...-Capacitor, DI...Diode, R2~R12 Resistor.

Claims (1)

[Claims] A power switch is installed on the input side of a power supply circuit that converts AC power into DC power and smoothes the DC power using a smoothing capacitor, and a relay contact is installed on one side of a discharge resistor connected to the output side of the power supply circuit. and a photocoupler, which is driven when the power switch is turned on, and a first photocoupler, which is activated in response to a signal from a differential circuit sent out in conjunction with the operation of the photocoupler, on the input side of the power supply circuit. A transistor, a second transistor controlled by a signal from an integrating circuit sent out in accordance with the operation of the first transistor, and a second transistor operated based on a signal outputted in accordance with the operation of the second transistor. , a relay control circuit comprising a relay capable of opening the relay contact.